When transplanting trees or shrubs from one location to another, digging the plant in preparation for moving is typically the most challenging part of the job. Mechanical tree spades are commonly used to remove and replant trees. A typical tree spade includes a number of blades mounted in a circular or square fashion to form a single large circumferential spade. Typically, a spade will contain four blades, but variations exist with anywhere from three to eight blades. The blades are typically driven hydraulically into the ground and collapsed around the root ball of the tree. The tree can then be lifted out of the ground and transported to a desired position.
A major difficulty with this procedure is the centering of the tree spade around the root ball both laterally and front to back. Proper centering on the root ball is important because it provides the least damage to the root system and the best chance for the tree to thrive in the replanted location. Current methods either involve additional personnel to guide the spade into position or rely on elaborate, expensive and complicated sensor mechanisms that produce analog or digital signals which must be processed and displayed in a meaningful manner.